Recent Development
4. MORE RECENT DEVELOPMENTS
Details listed in the previous chapters cover developments and activities of the LUSI mud-volcano from June 2006 to December 2008. Towards the end of this period there was a decline in heat transfer by steam and hot mud (see trends in Figure 5a). However, recent IKONOS satellite photos show again an increase in eruptive activity.
In February 2009 the high-standing semi-circular dam around the mud discharge centre (see Figure 3) was severely breached and could no longer be repaired.. The outpouring mud quickly filled the low lying ponds in the N and W sectors. By March 2009, the confining semi-circular dam had subsided and was flooded. Partly dried and drained ponds in the northern quadrant were flooded again, together with smaller enclaves along the W boundary dam (Figure 7). The total flooded area increased to c. 10 km2.
Figure 7: Satellite (IKONOS) photo (24.06.9) of the area flooded by the LUSI mud discharges.
A significant increase of the steam cloud volume Vc over the crater occurred in February 2009 if compared with values observed during the 2ndhalf of 2008. The diameter dm of the de-gassing mud ring around the crater also increased in size at the same time up to 150 m.
It was the largest diameter ever noticed, although some of the increase might have been caused by the sinking of the constraining semi-circular dam structure. It appears that highly active eruptive phases that have caused large dam breaches in the past or caused large increases in mud outflows, as indicated by the sudden increase in the diameter of the gas-charged mud ring, are associated with some long-term periodicity.
Large eruptive events with massive outpourings of mud have occurred, for example, in December 2006, during the first months of 2008, and again at the beginning of 2009.
Smaller (groundwater?) ponds have also appeared outside the outer, confining dams pointing to widening and deepening of the subsidence area. The wavelength of subsidence is now about 3.3 km indicating that compaction of deeper de-pressured sediments is occurring. It is likely that widening of the subsidence bowl will continue.